Pipetting aid

ABSTRACT

The invention relates to a pipetting aid for exerting suction on liquids. The usual previous &#34;Peleusball&#34; has disadvantages when handling and with regard to washing out. The object of the invention is to create a pipetting aid through constructive change, which is functionally safe and easy to handle and which at the same time allows uncomplicated cleaning of the inside. The new pipetting aid according to the invention consists of an elastic hollow body (1) with a larger ball-like central body (2), at which a first tubular attachment (3) and a second tubular attachment (4) is located, a third tubular attachment (5) leaving the said second tubular attachment (4) at an angle, and is characterized in that in the first tubular attachment (3) an easily removable check valve with particular constructive design is disposed as a first closure component (6), the valve, when the ball-like central body (2) is squeezed, allowing, without additional actuation, the compressed air from the inside of the hollow body into the outer atmosphere, but not vice versa, and at the same time the second and third closure component (7) and (8) in the corresponding attachment (4) and (5) adopting a position which prevents air from passing from the inside to the outside. A production process is also described.

The invention relates to a pipetting aid for exerting suction on andemptying of liquids in pipettes and a production process for thispipetting aid.

A multitude of pipettes are known from the prior art, which exertsuction on liquids and squeeze them out by means of a piston mechanism.Only a few technical solutions however are known for pipettes which arestill frequently used in laboratories as simple, cheap and easy tohandle measuring devices and in which the exertion of suction is carriedout by mouth or with a rubber ball (the pipetting aid), which can bedeaerated.

A suction cylinder for exerting suction on liquids in pipettes isdescribed in DE-A-2155239, the said cylinder surrounding the end of thepipette, without valves being provided for it. A practical transpositionof this suggestion is not known.

DE-A-3016594 describes a tubular pipette of fixed shape with a suctionaid, the suction aid consisting of an elastic, balloon-like containerpart, which has a suction opening and an aeration opening lying oppositeone another. The elastic and the container part of fixed shape can befused together and consequently form a pipette with a joined suctionpart. The closure components for the elastic container part are notspecified.

The German Utility Model GM 8333458 protects a pipetting aid forcapillary pipettes, said pipetting aid consisting of a bellow-like headand a following tube for receiving an adapter for the capillarypipettes. Openings for the entry and exit of air are not provided exceptvia the pipette tip.

A pipetting aid used under the name Peleusball is furthermore known (DE897 930), which consists of a rubber material with an inlet and outleteach closed by a ball valve in the form of a glass ball disposed in theair passage. A disadvantage of this pipetting aid is that it isdifficult to clean after pipetted liquids have entered into sections ofthe rubber material, and above all the necessity, when the air ball ispressed and likewise when pressing out residues from the pipette, ofsimultaneously having to actuate the corresponding valve with thefingers. A further disadvantage is the manufacture of at least twomoulding parts with the subsequent gluing together (or vulcanization) ofthe material.

The manufacture of such pipetting aids is mostly effected in theinjection moulding process whereby, due to the large balloon-likeenlargement of the central body, either the two separately injectionmoulded halves are glued together or vulcanized subsequently, or asingle-piece moulded body is produced in a mould without a core by meansof a propellant. With the lastly named process a very irregular surfaceof the elastic material is produced, which, after pipetted liquids haveentered, is difficult to clean.

The object of the invention is to develop a pipetting aid by using asimplified manufacturing process, which is functionally safe and easy tohandle and which at the same time allows uncomplicated cleaning of theinner area.

This object is achieved according to the invention by a pipetting aidfor exerting suction on liquids, consisting of an elastic hollow bodywith a larger ball-like central body at which are located a firsttubular attachment and a second tubular attachment, from which secondtubular attachment a third tubular attachment leaves at an angle, aneasily removable check valve as a first closure component being disposedin the first tubular attachment, which, when the ball-like central bodyis squeezed, allows, without further actuation, the compressed air frominside the hollow body into the outer atmosphere, but not vice versa andat the same time the second and third closure components in thecorresponding attachments substantially adopting a position whichprevents air from passing from the inside to the outside. When the airis compressed, the check valve therefore adopts a through passageposition, whilst having a closed or locked position when only lowpressure is in the lower central body.

The check valve is a cylindrical body in which at least one cylinderarea is closed over its entire area and the cylindrical body has, in itscylindrical part, at least one outlet or cavity suitable for the passageof air between the cylinder wall and the inner wall of the attachment.The cylindrical body here has a projecting, i.e. somewhat protrudingshoulder, which chamfers to the inner side of the cylindrical jacket atthe outer side of the lower cylindrical jacket.

The hollow body preferably consists of one single piece of a rubberelastic material. Furthermore, it is preferable that the diameter of thetubular first attachment is in a ratio of 1:2 to 1:4, preferably 1:2.5to 1:3.5, particularly 1:3.0 to 1:3.4 to the diameter of the ball-likecentral body.

In a first embodiment the check valve is a substantially rigidcylindrical body in which at least one area is closed over its entirearea and which has one or several cavities for the passage of air on theouter side of the cylindrical jacket which is towards the inner wall ofthe attachment. Through its seat in the elastic first tubularattachment, when the air is compressed in the inner ball-like centralbody, one or several passages are created between the valve body and theelastic inner wall of the attachment, said inner wall fitting closely inthe remaining part. The named cavities can, for example, be disposed asa continuous annular groove in the lower part of the cylinder, thus, forinstance, at the ball-like central body attachment, this attachmentcooperating with the projecting shoulder of the cylinder.

In a second embodiment, the check valve is a non-elastic cylindricalhollow body, the upper, outward pointing area of which is a closedprojecting lid and the hollow body comprising, in its cylindricaljacket, at least one, preferably two continuous bore(s) and the area ofthe said hollow body in the direction of the ball-shaped enlargementbeing open. Here, a projecting shoulder is located on the outside of thelower cylindrical jacket, said shoulder running conically to the innerside of the cylindrical jacket.

In order to allow the comfortable inserting and removing of the valve ofboth embodiments, a small tolerance of -0.3 mm should always be presentin the interaction between the valve and the inner side of the firstattachment, i.e. an exact press fit should be avoided. In so doing, thevalve is held such that, underneath the projecting upper area of itscylindrical jacket, an annular round groove is formed in the cylindricaljacket which contacts the annular round lip disposed at the inner upperedge of the attachment.

Alternatively the valve is held in that the projecting shoulder of theclosure component is disposed at a distance from the groove such that,when the lip contacts the groove, the annular surface of the shoulderrests positively at the attachment area of the ball-like central body.In so doing, the attachment area of the central body should have anangle of 90° to the first attachment.

The bore for the second embodiment in the cylindrical jacket is disposedunderneath the groove, but above the projecting shoulder, preferably ina section of the closure component nearer the groove. The cylindricaljacket preferably comprises two bores, which are preferably opposite oneanother.

With the help of this first closure component in the form of a checkvalve, perfect sealing is possible in the corresponding fitting withinthe first attachment, and the valve is easy to take out due, forexample, to the collar-shaped, enlarged upper part.

In the region where the third attachment runs into the secondattachment, a low-volume enlargement of the attachment is provided. Thisis used to completely squeeze out residual liquids which have remainedin the pipette. An enlargement of this kind at the end of the thirdattachment, as in the prior art, is therefore no longer required. Thereis also no need, in order to squeeze out residual liquids, tosimultaneously actuate the closure component located in the thirdattachment and this consequently illustrates a further improvement ofthe invention.

The second and third closure component should in each case be a ball,preferably a glass ball. It is likewise expedient to dispose circular,marked pressure surfaces raised relative to the round tubularattachment, on the outside of the second and third attachment, at theheight of the corresponding closure components.

The rubber-elastic material is advantageously a relatively inertmaterial relative to aggressive liquids like acids and bases, whichmaterial furthermore comprises a good extensibility and excellentelasticity or fatigue stability.

According to the invention natural rubber is preferred.

Through the special design of the first tubular attachment in relationto the ball-like central body and of the closure component (check valve)disposed in the attachment, the pipetting aid according to the inventionmakes it possible to easily take out the valve and to simply clean theelastic hollow body, for instance, of liquids or solids (withsuspensions). A further advantage is that due to the safety valve used,it is no longer necessary to also simultaneously actuate the valve inthe first attachment when the ball-like central body is squeezed, inorder to let the air into the outer atmosphere.

A further advantage is seen from the process described in the following.The process according to the invention for manufacturing a pipetting aidfrom rubber-elastic material, consists in that a thermoplastic mouldingmaterial is fed into a two-piece, closed mould in the conventionalmanner at a high temperature and is cross-linked, a multi-part mouldingcore, preferably a three-piece moulding core, being disposed inside themould, the hollow chamber formed by the inner surface of the outer mouldand the outer surface of the moulding core corresponding to a hollowbody with a ball-like central body, and a first tubular attachment, anda second tubular attachment disposed on the opposite side, from whichsecond tubular attachment a third tubular attachment leaves at an angle,and immediately following the removal from the two-piece mould, the partof the moulding core for the ball-like central body being removed byenlarging the first tubular attachment of the rubber-elastic hollowbody, the pipetting aid then being completed by inserting threecorresponding closure components into the three attachments.

The hollow body preferably consists of a single piece of arubber-elastic material in order to avoid additional working cycleswhich are necessary when putting together multi-piece hollow bodies.

It is furthermore advantageous for the diameter of the tubular firstattachment to be in a ratio of 1:2 to 1:4, preferably 1:2.5 to 1:3.5,particularly 1:3.0 to 1:3.4 to the diameter of the ball-like centralbody. By this means, a problem-free removal from the mould of themoulding core for the ball-like central body is possible by means of thefirst attachment, said attachment later receiving the safety valve.

The injection moulding process, which allows efficient production of theobject of the invention, is particularly suitable as the manufacturingprocess. The temperatures here are dependent upon the kind ofthermoplastic material. In general the temperature lies in the region of80° C. to 200° C., preferably in the region of 100° to 180° C. Pressureand dwelling time in the mould must also be matched to the correspondingthermoplastic material and lie in the region of professional knowledge.It is therefore also clear that other manufacturing processes like, forexample, the "transfer moulding" process can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail in the following by examples.In the corresponding drawing:

FIG. 1: is a sectional view of the hollow body according to theinvention

FIG. 2: is a partial section of the hollow body

FIG. 3: is a detailed section of the upper end of the first attachmentand of the safety valve

FIG. 4: is a detailed section of the lower end of the safety valve andof the attachment area of the ball-like central body

FIG. 5: is a sectional view of the check valve in the first embodiment.

EXAMPLE 1

The pipetting aid for exerting suction on liquids consists of arubber-elastic hollow body 1 made from natural rubber with a largerball-like central body 2, at which a first tubular attachment 3 and asecond tubular attachment 4 is located. A third tubular attachment 5leaves at an angle from the second attachment. In the first tubularattachment 3 an easily removable safety valve is disposed as a firstclosure component 6, which, when the ball-like central body 2 issqueezed, allows, without additional actuation, the compressed air frominside the hollow body into the outer atmosphere, but not vice versa. Atthe same time, during such actuation, the second and third closurecomponent 7 and 8, which are used here in the form of conventional glassballs, substantially adopt a position which prevents air passing fromthe inside to the outside in the corresponding attachment 4 and 5. Dueto this passage, specified in one direction only, the safety valveallows the vacuum which has occurred in the ball-like central bodythrough squeezing, to be used in the second attachment 4 after actuatingthe closure component 7, for exerting suction on air or liquid by meansof the pipette connected at the outer opening 23 of the attachment 4.

The diameter of the tubular first attachment 3 is in a ratio of 1:3.2 tothe diameter of the ball-like central body 2. In the attachment 3, thefirst closure component 6 is disposed as a safety valve in the form of anon-elastic cylindrical hollow body, the upper, outward pointing area 11of which is a closed protruding lid and the hollow body comprising inits cylindrical jacket 12 at least one continuous bore 13 and the area17 being open inside towards the ball-shaped enlargement. According toFIG. 4, there is located at the outer side of the lower cylindricaljacket 12 a projecting shoulder 14 which runs conically to the innerside 15 of the cylindrical jacket 12. By means of this conical shape,the insertion of the valve is facilitated. From FIG. 4 the preferredrectangular attachment area of the central body 2 and its contact withthe annular surface of the shoulder 14 can also be seen.

As seen from FIG. 3, an annular round groove 18 is formed in thecylindrical jacket 12 of the closure component 6 underneath theprojecting upper base 11 in the said jacket. At the inner upper edge ofthe attachment 3, an annular round lip 9 is disposed which engages thegroove 18.

The projecting shoulder 14 of the closure component 6 is disposed at adistance from the groove 18, such that when the lip 9 engages the groove18, the annular surface of the shoulder 14 rests positively at theattachment area of the ball-like central body 2.

In the embodiment of the closure component 6 with bore, the bore 13 isdisposed in the cylindrical jacket 12 closely beneath the groove 18. Itcan consist of two bores on opposite sides.

In the first embodiment, the closure component 6 is provided with agroove 19. When the ball-like central body 2 is squeezed, this closurecomponent, without additional actuation, by widening the attachment 3,allows the compressed air from inside the hollow body, via the groove19, along the outer wall of the cylindrical jacket 12 into the outeratmosphere, but not vice versa.

For pipettes not adjusted to drain off, it is necessary to remove theliquid residue through subsequent air pressure by means of the pipettingaid. For this purpose, a low-volume enlargement 10 of the attachment isprovided in the area where the third attachment 5 runs into the secondattachment 4.

According to FIG. 2, circular, marked pressure surfaces 21, 22 raisedrelative to the round tubular attachment, are disposed on the outside ofthe second and third attachment 4, 5 at the height of the correspondingclosure component 7, 8. These facilitate the actuation of the closurecomponents 7 and 8.

EXAMPLE 2

The process according to the invention consists in that a material madeof natural rubber is injected into a two-piece closed mould by means ofthe injection moulding process, a three-piece moulding core consistingof the moulding core for the attachment 3 with the ball-like centralbody 2 and the two moulding cores for the attachment 4 and theattachment 5 being disposed inside the said two-piece closed mould. Thetemperature here is approximately 150°-160° C. Immediately following theremoval from the two-piece mould, the moulding core for the ball-likecentral body is removed by enlarging the attachment 3 of thesingle-piece rubber-elastic hollow body. The pipetting aid is thencompleted by inserting the safety valve and the two glass balls asclosure components into the three attachments. The pipetting aidconsists of only one single piece and can be used without subsequentwork.

We claim:
 1. A pipetting aid for exerting suction on liquids, saidpipetting aid comprising:(a) a hollow elastic body (1), (b) a hollowelastic generally ball-shaped portion (2) formed as part of said hollowbody (1), the interior of said ball-shaped portion (2) communicatingwith the interior of said body (1), (c) a first hollow tubular portion(3) connected to said ball-shaped portion (2), the interior of saidfirst tubular portion (3) communicating with the interior of saidball-shaped portion (2), (d) a second hollow tubular portion (4)connected to said ball-shaped portion (2), the interior of said secondtubular portion (4) communicating with the interior of said ball-shapedportion (2), (e) a third hollow tubular portion (5) connected at anangle to said second tubular portion (4), the interior of said thirdtubular portion (5) communicating with the interior of said secondtubular portion (4), (f) first check valve means (6) positioned in saidfirst tubular portion (3) and adapted to permit the passage of air frominside said ball-shaped portion (2) to the atmosphere upon compressionof said ball-shaped portion (2) and not in the reverse direction, (g)second check valve means (7) positioned in said second tubular portion(4), (h) third check valve means (8) positioned in said third tubularportion (5), (i) said second check valve means (7) and said third checkvalve means (8) being arranged within said second and third tubularportions (4) and (5) respectively so as to prevent the passage of airfrom inside said ball-shaped portion (2) to the atmosphere uponcompression of said ball-shaped portion (2), (j) said first check valvemeans being in the form of a hollow cylinder (12), (k) closure means(11) extending across and closing that end of said hollow cylinder (12)remote from said ball-shaped portion (2), (l) air passage meansextending into the external periphery of said hollow cylinder (12) topermit the passage of air between the external periphery of said hollowcylinder (12) and the internal periphery of said first tubular portion(3).
 2. A pipetting aid as in claim 1, wherein:(m) said air passagemeans comprises a bore (13) extending through the wall of said hollowcylinder (12) and communicating between the interior of said hollowcylinder (12) and the internal periphery of said first tubular portion(3).
 3. A pipetting aid as in claim 1, wherein:(m) said air passagemeans comprises a groove (19) extending around the external periphery ofsaid hollow cylinder (12).
 4. A pipetting aid as in claim 1, furthercomprising:(m) a conical cross-section provided at that end of saidhollow cylinder (12) remote from said closure means (11), said conicalcross-section increasing in dimension toward said closure means (11). 5.A pipetting aid as in claim 1, wherein:(m) said hollow elastic bodyincluding said ball-shaped portion (2) and said first, second and thirdtubular portions (3), (4) and (5) are of unitary one-piece construction.6. A pipetting aid as in claim 1, wherein:(m) the ratio of the internaldiameter of said first hollow tubular portion (3) to the maximuminternal diameter of said ball-shaped portion (2) is in the range of 1:2to 1:4.
 7. A pipetting aid as in claim 1, wherein:(m) the ratio of theinternal diameter of said first hollow tubular portion (3) to themaximum internal diameter of said ball-shaped portion (2) is in therange of 1:2.5 to 1:3.5.
 8. A pipetting aid as in claim 1, wherein:(m)the ratio of the internal diameter of said first hollow tubular portion(3) to the maximum internal diameter of said ball-shaped portion (2) isin the range of 1:3.0 to 1:3.4.
 9. A pipetting aid as in claim 1,wherein:(m) said closure means (11) projects outwardly around and beyondthe external periphery of said hollow cylinder (12), said pipetting aidfurther comprising:(n) a groove (18) formed around the externalperiphery of said hollow cylinder (12) below that portion of saidclosure means (11) projecting beyond the external periphery of saidhollow cylinder (12), (o) an inwardly projecting lip (9) formed aroundthe internal periphery of said first tubular portion (3) and extendinginto said groove (18).
 10. A pipetting aid as in claim 1, furthercomprising:(m) a shoulder (14) on the external periphery of said hollowcylinder (12) adjacent the widest portion of said conical cross-section,said shoulder projecting outwardly from the external periphery of saidhollow cylinder (12) and having an upper surface, wherein:(n) thedistance between said shoulder (14) and said groove (18) is such thatwhen said lip (9) engages said groove (18), that part of ball-shapedportion (2) adjacent the vicinity of juncture thereof with said firsttubular portion (3) rests on the said upper surface of said shoulder(14).
 11. A pipetting aid as in claim 1, further comprising:(m) anenlarged portion (10) formed in said second tubular portion (4) adjacentthe juncture thereof with said third tubular portion (5), the volume ofsaid enlarged portion (10) being less than the volume of saidball-shaped portion (2).